| Name: Thouheeda Beegum RV |
| Affiliation: PHD |
| Conference ID: ASI2026_798 |
| Title: SPECTRO-POLARIMETRIC ANALYSIS OF PROMPT EMISSION OF GRB231129C |
| Abstract Type: Poster |
| Abstract Category: High Energy Phenomena, Fundamental Physics and Astronomy |
| Author(s) and Co-Author(s) with Affiliation: Dr. Vidushi Sharma(UMBC Univ. of MD, Baltimore County,USA), Thouheeda Beegum RV(Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Thiruvananthapuram ,695551, India), Dr. Shabnam Iyyani(Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM), Thiruvananthapuram ,695551, India), Rushikesh Digambar Sonawane(cation and Research Thiruvananthapuram (IISER TVM), Thiruvananthapuram ,695551, India) |
| Abstract: A spectro–polarimetric analysis of the bright gamma-ray burst GRB 231129C is presented using observations from Fermi–GBM, Fermi–LAT, and AstroSat–CZTI. A fluence of (8.41±0.04)×10^−5 erg cm^−2 in the 10–1000 keV energy band, measured over a T90 duration of 5.8s, placing it among the brightest GRBs detected by Fermi. A Band plus blackbody model with an extra power-law component is preferred by time-integrated spectral analysis, indicating that LAT (> 100 MeV) represents the onset of afterglow emission. Time-resolved spectroscopy reveals that the prompt emission is best described by a CPL plus blackbody model with a thermal component that contributes 10%–40% of the overall flux and is observed up to 5 sec. In the absence of a direct spectroscopic measurement, the redshift of the burst is estimated to be z = 0.52 using the Amati correlation. Using LAT data, we infer that the radiative efficiency is nearly 44% of the total jet energy released as radiation during the prompt phase. The spectral characteristics are explained within the paradigm of a dissipative photosphere, where a fraction of the thermal emission advected from deep inside the outflow is upscattered to higher energies via the high-energy electrons produced in the dissipation site below the photosphere. The time-integrated and time-resolved polarization analyses of the burst, conducted using the CZTI data, yield no significant polarization detection in the 100–600 keV energy range, with an upper limit of PF < 24%. Thus, the observed emission is consistent with intrinsically unpolarized dissipative photospheric radiation, since the relativistic beaming cone (1/Γ) along the line of sight (θᵥ) is much narrower than the jet opening angle (θj), corresponding to either an on-axis configuration (θv/θj <1.3) or a marginally off-axis view (1.3≤ θv/θj ≤1.5). |
